The present invention relates to gas turbine blades or buckets and more particularly relates to a turbine blade tip cap with a number of cooling holes therein.
Gas turbine components are exposed to the very high temperatures of the combustion gas flow therethrough. The components generally are cooled by a means of a cooling airflow so as to maintain structural integrity and promote longevity. Efficient use of the cooling airflow not only may prolong the life of the turbine blades but also may promote overall lower engine operating costs.
The gas turbine blades or buckets pose a particular technical challenge for cooling. The tip portion generally includes a tip cap and also may include a tip squealer extending radially away from the tip cap. The tip squealer provides rub tolerance in the event that the tip clearance is diminished during turbine operation. The tip squealer further increases the challenge of cooling the tip because access to the squealer generally is limited.
Known cooling methods generally include several cooling holes positioned within the tip cap. The holes generally extend from a cooling passage or passages within the blade through the tip cap. The stresses and high temperatures present during normal operation of the turbine, however, may cause excessive oxidation, cracking, and creep bulging in the known tip caps.
In addition to cooling, the holes in the tip cap allow dust in the blade to vent. This venting also may improve overall efficiency. The tip cap also serves to close the blade core. Such closure is required for casting.
There is a desire, therefore, to optimize the shape of the tip cap. The tip cap may optimize the cooling fluid flow therethrough, allow dust to vent, and provide improved material characteristics.